Custom forEach, map, reduce | Dataford Interview Questions

Code a bespoke version of forEach, map, and reduce.

Implement one Python function that selects the requested operation and applies a named callback without using Python's built-in map, filter, reduce, or list comprehensions. The function must preserve order, avoid mutating the input, return None for forEach, and support an optional initial accumulator for reduce.

Contract

def bespoke_array_methods(values, operation, callback, initial=None): accepts integer arrays, an operation of forEach, map, or reduce, and callbacks named identity, double, add, or multiply.

Constraints

0 <= len(values) <= 10^4
values contains integers
operation is one of "forEach", "map", or "reduce"
callback is one of "identity", "double", "add", or "multiply"
reduce inputs are non-empty when no initial value is supplied
Do not use built-in map, filter, reduce, or list comprehensions
The input list must not be modified

Function Signature

def bespoke_array_methods(values, operation, callback, initial=None):

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